Every people deserve their own nation (Serbs included).
Sorting this out is often bloody, and the innocent suffer the most.
That does not make the process or the result criminal. It’s just the way things always have been, and always will be.
It always depends on the definition of "their". In too many cases (Palestinians being the most visible example) a small cabal of gangsters figures out how to adopt the mantle of "an oppressed people" and work the international community for aid and and arms, all while delivering greater oppression to the people of "their" territory than the supposed occupiers do.